The need of producing power beyond the traditional ways such as the ones based on fossil fuels or renewable energies has driven a great development of the so called “renewable energies” such as solar power, wind power, power obtained from waves or currents, etc.
However, in the case of power generation in facilities located in seas or lakes, the development of systems which allow transporting the power produced from the power collecting device generating it to a connection point of a distribution network on land is necessary to enable harnessing it. Additionally, it is essential that the power collecting device can be connected to and disconnected from said network for allowing its transfer to land for the purpose of performing repair work, maintenance, protection against storms, etc.
A common configuration is that in which there is an underwater electric cable which is connected at one end to the marine energy collector, while the other end is connected to a connection point of a power distribution network located on land.
However, some of these marine energy collectors do not convert marine energy directly into electricity, but act on a hydraulic or pneumatic system, generating a certain pressurised fluid flow which needs to be transported to another location, be it to the sea or the land, where that pressurised fluid flow is converted into electricity by means of the appropriate equipment.
It is also usually necessary to transmit data between the marine energy collector and another location, such that the system operation can be monitored, or remotely act on the equipment of these marine energy collectors.
For this purpose, there are flexible hoses containing therein conduits for channelling fluids, electric cables for transporting power, data transmitting systems such as optic fibres, or any combination of the preceding elements. These flexible hoses are called “umbilicals” (or umbilical cables) and allow physically connecting the marine energy collector with land in terms of power, fluids, and data level.
Another clearly distinctive aspect of this type of renewable marine energy is that, the collectors of this energy need a high level of maintenance and inspection due to the marine environment in which they work. Sometimes, they are only installed in their position for a few days or weeks, for the purpose of verifying their performance against certain circumstances. Other times, due to unforeseen malfunctions or storm threats, it is necessary to quickly remove them from their position to take them to the port. Installing or removing a marine energy collector on/from its location in the sea, due to the causes indicated above, always entails connecting or disconnecting the umbilical associated by means of a suitable connector which is inserted in the umbilical for such purpose.
Thus, connecting or disconnecting this umbilical and therefore the electric cables, optic fibre or fluid conduits must be able to be performed quickly and is designed for the possibility that this handling is done frequently.
Another feature to be considered is that several umbilicals originating from the marine energy collectors are commonly required to be independently interconnected in a single underwater hose or delivery umbilical which concentrates all the generated power and data for their transmission to land. The underwater layout of the delivery hoses or umbilicals is thus significantly simplified. Instead of installing as many umbilicals as there are power collectors in a certain location on land, it is only necessary to lay a single delivery hose or umbilical which concentrates all the power and data from different collectors.
Thus, a typical configuration of a marine energy collecting farm is that described in FIGS. 11 and 12 wherein an group of marine energy collectors is depicted which power and data are concentrated, by means of their umbilicals, in an interconnection device for transmitting these to land by means of a single delivery hose. That delivery hose is usually connected to the power network through a power sub-station on land. Connectors inserted in said umbilical are used for connecting and disconnecting the umbilical.
Elements capable of performing two differentiated functions in a collecting farm are thus necessary:
1.—Connecting and disconnecting the umbilicals for removing the energy collector devices, underwater connectors being used to that end.
2.—Interconnecting the power and data for concentrating and delivering them to land in a single hose or umbilical, an interconnection device being used to that end.
It should be pointed out that the connectors inserted in the umbilical are expensive elements since they are designed to enable connecting and disconnecting medium- and high-voltage electric cables in a marine environment as well as to enable using them frequently.
In general, the devices capable of interconnecting several umbilicals must be installed on the seabed at considerable depths, since it is there that lower stresses due to marine agents such as swell, currents or wind have to be endured.
Therefore, as the depth at which these interconnection devices are installed increases, the layout of the umbilicals that usually rest on the seabed which must be interconnected, also runs at greater depth. This complicates the underwater interconnection of these umbilicals since the underwater work with divers at depths greater than 50 meters is difficult, and practically impossible at depths greater than 100 meters.
From said depths onwards the use of underwater robots is necessary, increasing the cost and the connection or disconnection work operation time tremendously, therefore this option does not work for a case such as that described, with frequent operations in a quick and simple manner. To avoid the use of divers and underwater robots there are interconnection systems which allow its removal from the seabed to the surface to enable carrying out the necessary connection and disconnection operations. It is necessary to pay special attention to the removal operation of the interconnection device from the seabed in the case of two or more umbilicals interconnected to one another, since when attempting to raise the equipment to the surface both the umbilicals and the equipment can suffer stresses due to tightening of the umbilicals, such that any of the components can be seriously damaged. Similarly, the umbilicals can become entangled with one another or the equipment can land on the umbilicals when replacing the interconnection device on the seabed since these will reach the bottom first, with the consequent damage this entails.
It is also necessary that each umbilical originating from a marine energy collector can be disconnected from the interconnection device independently from the rest of the umbilicals connected to this interconnection device, shall it is necessary to remove a single marine energy collector from its location for maintenance.
Another important aspect in the field of marine energy collectors is that power protection equipment, flow regulating equipment, switching equipment, measuring apparatuses or any other device can be located in the interconnection element, such that in case of malfunction a single unit can be disconnected individually from the power circuit, hydraulic circuit or data transmission circuit or measurements of the quality and amount of electric current supplied or of the flow of the fluid supplied or of the signals sent can be taken or any other action can be carried out on a single umbilical without interfering the operation of the rest of the marine energy collectors connected to the interconnection device.
EP 2,237,380 shows an interconnection system for interconnecting underwater cables capable of being raised to the surface. However, said system does not allow the individual and independent removal of each electric cable. Furthermore, it does not solve the aforementioned problems of tightening during removal and the problems of depositing the interconnection device on top of the electric cables. Inserting electric apparatuses as those described in an individual and independent manner in each electric cable is also not possible with this system.
Several similar solutions which further use terminals such as those normally used on land considerably reducing the price of the device are also known in the state of the art. Nevertheless, the way in which the electric cables penetrate the device requires an “in situ” preparation of the electric terminals as well as of the mechanisms rendering leak-tightness to the conduits when they penetrate the connection chamber, therefore the connecting and disconnecting operation is slow and is not intended to be done frequently.
Therefore in the state of the art of marine energy generation systems, there is not an interconnection system and method based on interconnection devices which can be raised to the surface, which allow connecting and disconnecting umbilicals in a simple and independent manner and assuring the integrity of all the elements involved during the raising and subsequent placing of the same.